#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <climits>
#include <iomanip>
#include <cmath>
#include <string>
#include <vector>
#define int long long
#define x first 
#define y second 
using namespace std;
const int N = 1e5 + 10;
int a[N];
void solve()
{
    int x,y,w,k;
    cin >> x >> y >> w >> k;
    int d = 0;
    int ans = 0;
    while(ans < k)
    {
        d++;
        if(d < x)
        {
            ans += floor(d * 1.0 / w * 1.0);
        }
        else  
        {
            ans += floor(d * 1.0 / w * 1.0) + y;
        }
    }
    cout << d << endl;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr),cout.tie(nullptr);
    int t = 1;
    /*  int t;
     cin >> t; */
    while(t -- ) solve();
    return 0;
}